CN114920206A - Process for removing siloxane in dilute sulfuric acid by continuous method - Google Patents
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- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 title claims abstract description 277
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 title claims abstract description 48
- 238000000034 method Methods 0.000 title claims abstract description 33
- 230000008569 process Effects 0.000 title claims abstract description 28
- 238000011437 continuous method Methods 0.000 title abstract description 8
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 67
- 230000003647 oxidation Effects 0.000 claims abstract description 53
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 claims abstract description 52
- 238000004519 manufacturing process Methods 0.000 claims abstract description 24
- 238000001914 filtration Methods 0.000 claims abstract description 21
- 230000001590 oxidative effect Effects 0.000 claims abstract description 20
- 229940050176 methyl chloride Drugs 0.000 claims abstract description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910004298 SiO 2 Inorganic materials 0.000 claims abstract description 17
- 239000007800 oxidant agent Substances 0.000 claims abstract description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 6
- 239000000843 powder Substances 0.000 claims abstract description 4
- 239000001117 sulphuric acid Substances 0.000 claims abstract description 4
- 235000011149 sulphuric acid Nutrition 0.000 claims abstract description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 24
- 229910002804 graphite Inorganic materials 0.000 claims description 24
- 239000010439 graphite Substances 0.000 claims description 24
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 21
- 238000010438 heat treatment Methods 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 7
- 239000007789 gas Substances 0.000 claims description 7
- 210000003298 dental enamel Anatomy 0.000 claims description 2
- 239000012286 potassium permanganate Substances 0.000 claims description 2
- 239000004809 Teflon Substances 0.000 claims 1
- 229920006362 Teflon® Polymers 0.000 claims 1
- 230000008901 benefit Effects 0.000 abstract description 8
- 238000003912 environmental pollution Methods 0.000 abstract description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 15
- 239000012535 impurity Substances 0.000 description 15
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 9
- 239000002253 acid Substances 0.000 description 9
- -1 polytetrafluoroethylene Polymers 0.000 description 9
- 229910001868 water Inorganic materials 0.000 description 8
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 7
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- 239000005416 organic matter Substances 0.000 description 7
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 7
- 239000004810 polytetrafluoroethylene Substances 0.000 description 7
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 7
- 230000015572 biosynthetic process Effects 0.000 description 6
- 239000004744 fabric Substances 0.000 description 6
- 238000003786 synthesis reaction Methods 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 5
- 238000010924 continuous production Methods 0.000 description 5
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 4
- NEHMKBQYUWJMIP-NJFSPNSNSA-N chloro(114C)methane Chemical compound [14CH3]Cl NEHMKBQYUWJMIP-NJFSPNSNSA-N 0.000 description 4
- 238000003795 desorption Methods 0.000 description 4
- 238000006460 hydrolysis reaction Methods 0.000 description 4
- 239000000047 product Substances 0.000 description 4
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- 230000009471 action Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
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- 239000000178 monomer Substances 0.000 description 3
- 230000002035 prolonged effect Effects 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- HRYZWHHZPQKTII-UHFFFAOYSA-N chloroethane Chemical compound CCCl HRYZWHHZPQKTII-UHFFFAOYSA-N 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- LIKFHECYJZWXFJ-UHFFFAOYSA-N dimethyldichlorosilane Chemical compound C[Si](C)(Cl)Cl LIKFHECYJZWXFJ-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 229960003750 ethyl chloride Drugs 0.000 description 2
- 239000000945 filler Substances 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 238000007086 side reaction Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000002912 waste gas Substances 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 229910018557 Si O Inorganic materials 0.000 description 1
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical group [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 description 1
- 238000005903 acid hydrolysis reaction Methods 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- YGZSVWMBUCGDCV-UHFFFAOYSA-N chloro(methyl)silane Chemical compound C[SiH2]Cl YGZSVWMBUCGDCV-UHFFFAOYSA-N 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
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- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000004451 qualitative analysis Methods 0.000 description 1
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- 150000003254 radicals Chemical class 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 150000003377 silicon compounds Chemical class 0.000 description 1
- 239000011863 silicon-based powder Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
Images
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/90—Separation; Purification
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/90—Separation; Purification
- C01B17/905—Removal of organic impurities
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention relates to a process for removing siloxane in dilute sulfuric acid by a continuous method, which comprises the following steps: (a) stripping: dilute sulfuric acid is added into the stripping tower from the upper part of the stripping tower, low-pressure steam is continuously introduced from different positions of the middle part and the lower part of the stripping tower, and oxidation reaction is carried out on organic matters and siloxane; (b) and (3) oxidation: continuously feeding the stripped dilute sulfuric acid into an oxidation kettle, continuously adding an oxidant, oxidizing residual organic matters and siloxane to generate CO 2 、H 2 O and SiO 2 (ii) a (c) Concentrating: continuously adding the oxidized dilute sulfuric acid into a concentration tower from the middle part of the tower, introducing nitrogen from the lower part of the tower, and obtaining concentrated sulfuric acid at the tower kettle; (d) and (3) filtering: continuously filtering the concentrated sulfuric acid to obtain colorless and transparent concentrated sulfuric acid and white SiO 2 And (5) powder, and returning the obtained concentrated sulfuric acid to the methyl chloride production for continuous utilization. The invention reduces the environmental pollution by continuously removing the siloxane in the dilute sulphuric acid, and has obvious economic benefit and ringAnd (5) benefit conservation.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a process for removing siloxane in dilute sulfuric acid by a continuous method.
Background
In the production process of organic silicon, methyl chloride is one of main raw materials of methyl chlorosilane mixed monomers, and methyl chloride is generated by the reaction of methanol and hydrogen chloride.
In order to improve the chlorine utilization rate in production, the synthesis of the chloromethane mainly adopts hydrogen chloride gas generated in the process of pressurizing and hydrolyzing concentrated acid by dimethyldichlorosilane, and the hydrogen chloride gas is subjected to vapor-liquid separation, conveyed to a chloromethane reaction kettle by a pipeline and reacts with methanol under the action of a catalyst to generate the chloromethane. Although the hydrogen chloride gas generated by the pressurized concentrated acid hydrolysis of the dimethyldichlorosilane is subjected to vapor-liquid separation, trace siloxane is carried in the synthesis process of dechloromethane. Thus, concentrated sulfuric acid also removes siloxane from methyl chloride when drying impurities such as methyl chloride moisture. The concentrated sulfuric acid can reduce the impurity adsorption efficiency of the methyl chloride along with the prolonging of the time for treating the methyl chloride and can not be used any more, so a large amount of dilute sulfuric acid is formed. With the continuous expansion of organosilicon monomer production facilities, diluted sulfuric acid will be more and more, and can no longer be used for production, only can sell. In order to reduce the production cost, protect the environment and not pollute the environment, siloxane and the like in the waste gas are removed, sulfuric acid is recovered, the waste gas is recycled, the production cost of the chloromethane is reduced, meanwhile, the continuous process has large process treatment capacity and high automatic operation degree, no secondary industrial waste is generated in the treatment process, the pollution to the environment is reduced, and the method has obvious economic benefit and environmental protection benefit.
CN110642229A discloses a mixed desorption purification process of siloxane-containing hydrochloric acid and organic-containing sulfuric acid, which comprises the following steps: (1) mixing siloxane-containing hydrochloric acid, organic matter-containing sulfuric acid and concentrated sulfuric acid, hydrolyzing sulfuric acid organic matter into sulfuric acid, easily separating organic matter, and stripping and separating out partial hydrogen chloride gas to obtain siloxane-containing mixed acid; (2) the mixed acid is subjected to solid-liquid separation to remove solid polymer. The mixing, resolving and purifying device for the siloxane-containing hydrochloric acid and the organic matter-containing sulfuric acid comprises a mixer, a hydrolysis kettle and a filter. The process comprises subjecting siloxane-containing hydrochloric acid, organic-containing sulfuric acid and a mass of sulfuric acid to a reverse hydrolysis reaction in a tower filled with a filler, wherein the hydrolysis of the organic-containing sulfuric acid produces lumpy solids according to the reaction phenomenon mentioned in the patent, and the tower is clogged if the tower is filled with the filler.
Moreover, the solid polymer generated after liquid-solid separation can cause secondary environmental pollution, and the treatment cost is increased; and the hydrogen peroxide added into the concentrated sulfuric acid further oxidizes impurities, and the unreacted hydrogen peroxide enters a methyl chloride production system along with the recycling of the sulfuric acid, so that the methyl chloride is oxidized to generate more organic impurities, and the subsequent silicon powder and the methyl chloride are synthesized into a crude monomer to cause adverse effects and generate more high-boiling-point organic silicon compounds without economic values.
CN111792627A discloses a method for recovering sulfuric acid waste liquid in chloromethane production process, which adopts an intermittent treatment process to treat the sulfuric acid waste liquid by three steps of steam stripping, filtering and concentration, and obtains the sulfuric acid waste liquid with the concentration of more than 98 wt%, the COD value of less than 400ppm, SiO and other impurities after removing the organic matters and other impurities in the sulfuric acid waste liquid 2 The content of sulfuric acid is less than 100 ppm. Although the treated sulfuric acid can be used for the production of methyl chloride synthesis, the COD value and SiO 2 The content is still high, and residual organic matters can also react with hydrogen chloride in the production process to produce chloralkane; SiO 2 2 The materials are carried out in the production process, which can cause the blockage of subsequent production equipment and shorten the synthesis production time of the methyl chloride. And in order to prevent blockage, the intermittent treatment is necessary, which wastes manpower and material resources and is not suitable for the large-scale production process. Therefore, if the COD value and SiO in the sulfuric acid are reduced 2 The content of the sodium chloride is directly used for recycling, which is a technical problem to be solved urgently at present.
The invention is improved on the basis of the prior art, and adopts a continuous method to feed and discharge, and adopts four steps of stripping, oxidation, concentration and filtration to treat dilute sulfuric acid. Because the oxidation process is added, the COD value in the treated sulfuric acid is less than 120ppm, SiO 2 In the content ofLess than 50ppm is more beneficial to the synthesis of chloromethane, and the continuous method is adopted to treat dilute sulfuric acid, so that the treatment capacity is large, the automatic operation degree is high, and the production time is greatly shortened.
Disclosure of Invention
The invention aims to provide a process for removing siloxane in dilute sulfuric acid by a continuous method, which describes that the sulfuric acid content of the dilute sulfuric acid to be treated is 60-75 wt%, wherein the siloxane content is 4000-10000 ppm (by SiO) 2 Calculated), and 20-35% of water.
After the dilute sulfuric acid is subjected to the steps of steam stripping, oxidation, concentration, filtration and the like, the concentration is more than 98 percent, and the content of organic matter COD is less than<120ppm (preferably less than 80ppm), SiO 2 In an amount of less than<50ppm (preferably less than 30ppm) sulfuric acid. The treated sulfuric acid is recycled in the production of the methyl chloride, so that the production cost of the methyl chloride is reduced, the pollution to the environment is reduced, and obvious economic benefit and environmental protection benefit are achieved.
Aiming at the defects of the prior art, the invention provides a process for removing siloxane in dilute sulfuric acid by a continuous method, which comprises the following steps:
(a) steam stripping: dilute sulfuric acid is added into a stripping tower from the upper part of the stripping tower, low-pressure steam is continuously introduced from different positions of the middle part and the lower part of the stripping tower, and oxidation reaction is carried out on organic matters and siloxane by utilizing the self-oxidizing property of the sulfuric acid to remove most of the organic matters and the siloxane;
(b) and (3) oxidation: continuously feeding the stripped dilute sulfuric acid into an oxidation kettle, continuously adding an oxidant, and further oxidizing residual organic matters and siloxane to generate CO 2 、H 2 O and SiO 2 ；
(c) Concentrating: after the oxidation reaction, the dilute sulfuric acid flowing out of the oxidation kettle is continuously added into the tower from the middle part of the concentration tower, nitrogen is introduced from the lower part of the concentration tower, so that the moisture in the dilute sulfuric acid is brought out from the top of the tower, and the concentrated sulfuric acid is obtained from the tower kettle;
(d) and (3) filtering: continuously filtering the concentrated sulfuric acid to obtain colorless and transparent concentrated sulfuric acid and white SiO 2 And (3) powder, and returning the obtained concentrated sulfuric acid to the methyl chloride production for continuous utilization.
Preferably, the stripping column of step (a) is a graphite column.
Preferably, the stripping temperature of the step (a) is 100-180 ℃, and preferably 110-140 ℃.
Preferably, the addition amount of dilute sulfuric acid in the stripping reaction of the step (a) is 0.1-5 m 3 H, preferably 0.5 to 1m 3 /h。
The gas of the low-pressure steam of the stripping tower is water steam.
Preferably, the low-pressure steam pressure in the stripping reaction of the step (a) is 2-8 Kg/cm 3 。
Particularly, the low-pressure steam is 2-8 Kg/cm at the middle part and the lower part of the stripping tower 3 Entering a stripping tower; the middle position is at about position 1/2, the stripper bottoms 2/5 to 3/5, and the lower position is at bottoms 1/5-1/3. In a preferred embodiment, low-pressure steam is continuously introduced into the middle and lower parts of the stripping tower at the same time, and the pressure of the low-pressure steam in the middle part is 2-5Kg/cm 3 The pressure of the lower part is continuously introduced into the reactor at 5-8Kg/cm 3 The pressure of the low-pressure steam at the lower part is 1-3Kg/cm higher than that of the low-pressure steam at the middle part 3 。
The low-pressure steam respectively flows from different positions at the middle lower part of the stripping tower, so that the contact time of the low-pressure steam and the sulfuric acid is prolonged, and the stripping efficiency is improved. And the corrosion caused by local crystallization, condensation and the like in equipment or a pipeline can be reduced by entering from different positions, the use efficiency of the equipment is improved, the maintenance cost of the equipment is reduced, the service life of the equipment is prolonged, and the technical problem of the reduction of the stripping efficiency caused by corrosion aging is solved. According to the invention, through the treatment of pressure gradient, the low-pressure steam is contacted with the sulfuric acid in the stripping process for full stripping, so that the mass transfer strength and the desorption efficiency are improved, and therefore, the high-pressure steam stripping device still has high stripping efficiency even at a low stripping temperature (for example, below 120 ℃), and meanwhile, the energy consumption and the equipment aging risk are reduced.
Preferably, the oxidation reaction kettle in the step (b) is made of enamel or polytetrafluoroethylene lining.
Preferably, the oxidant in step (b) is selected from hydrogen peroxide or potassium permanganate.
Preferably, the dosage of the hydrogen peroxide in the step (b) is 50-300% of the mass of the siloxane, and preferably 100-150%.
Or the dosage of the hydrogen peroxide is 1 to 10 percent of the mass of the raw material dilute sulfuric acid.
Preferably, the flow rate of the dilute sulfuric acid stripped in the step (b) added into the oxidation kettle is 0.1-3 m 3 H, preferably 0.5 to 1m 3 H is the ratio of the total weight of the catalyst to the total weight of the catalyst. The oxidant is added at a flow rate of 0.01-0.4 m 3 H, preferably 0.02 to 0.05m 3 /h。
Preferably, after the oxidation reaction in the step (b), the flow rate of the dilute sulfuric acid flowing out of the oxidation kettle is 0.1-4 m 3 H, preferably 0.5 to 1m 3 /h。
Preferably, the oxidation temperature in the step (b) is 100-160 ℃, and the temperature is kept for 1-3 h.
More preferably, the oxidation in step (b) is performed by first heating to 100-120 ℃ and maintaining the temperature for 0.5-1h, and then heating to 130-160 ℃ and maintaining the temperature for 1-2 h.
The oxidation step controls staged temperature rise, and the control of temperature and time is beneficial to forward oxidation reaction, so that the oxidation reaction is more sufficient, oxidation products are more easily taken out, the occurrence of carbonization side reaction is reduced, the chroma of sulfuric acid is improved, and the oxidation efficiency is higher.
Preferably, the concentrated sulfuric acid of step (c) is sulfuric acid with a content of more than 98 wt%.
Preferably, the temperature of the concentration tower in the step (c) is 170-230 ℃, and preferably 180-190 ℃.
Preferably, the flow rate of the dilute sulfuric acid added in the step (c) is 0.1-5 m 3 H, preferably 0.5 to 1m 3 /h。
Preferably, the nitrogen flow rate in the step (c) is 10-100 m 3 Preferably 20 to 30 m/h 3 /h。
Preferably, in the step (d), the filter cloth is made of polypropylene or polytetrafluoroethylene.
The invention has the beneficial effects that:
(1) the invention treats dilute sulfuric acid through the steps of stripping, oxidizing, concentrating, filtering and the like to remove organic matters, siloxane and other impurities in the dilute sulfuric acid to obtain the dilute sulfuric acidSiO with the concentration of more than 98 percent 2 Sulfuric acid in an amount of less than 50 ppm.
(2) The invention utilizes steam stripping and oxidation, adopts normal pressure environment, adds a vent cooler, has no sulfuric acid in tail gas, and oxidizes siloxane into CO 2 、H 2 O and SiO 2 The method has no influence on the environment, and the acid-containing wastewater generated in the treatment process continuously returns to the concentration process and is continuously concentrated.
(3) The invention adopts tower-type steam stripping method to treat dilute sulfuric acid, so that siloxane and organic matter are oxidized into CO 2 、H 2 O and SiO 2 (ii) a Because the oxidant is adopted to further oxidize the dilute acid, the COD value in the sulfuric acid is less than 120ppm (even less than 80ppm), and the SiO value is 2 In an amount of less than<50ppm (more preferably less than 30ppm) reaches the quality index of fresh concentrated sulfuric acid.
(4) The invention adopts the continuous process to treat the dilute sulfuric acid, has high automation degree, simple operation, large treatment capacity and low treatment cost, and greatly shortens the production time. The filtered concentrated sulfuric acid has lower COD value and siloxane content, so that the production of chloromethane synthesis is facilitated, and the production period of equipment is prolonged.
(5) The invention adopts graphite material, low-pressure steam is introduced from different parts of the middle lower part of the tower and fully contacts with dilute sulfuric acid, and the oxidizing property of the dilute sulfuric acid at high temperature is utilized to oxidize silica into water, carbon dioxide and silica, thereby reducing the blocking phenomenon; further, under the action of gradient pressure, low-pressure steam is in contact with sulfuric acid to be fully stripped, so that the mass transfer strength and desorption efficiency are improved.
(6) According to the oxidation process, the siloxane can be oxidized to obtain the white carbon black, the hydrolysis of byproducts is promoted, and the purity of sulfuric acid is improved; the addition of a small amount of catalyst can promote the improvement of the free radical oxidation effect and the COD degradation effect.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and not to limit the invention. Wherein,
FIG. 1 is a flow diagram of the continuous process for removing siloxane from dilute sulfuric acid of example 1;
FIG. 2 is an IR spectrum of the filtered residue collected in example 1.
1. Dilute sulfuric acid; 2. low-pressure steam; 3. a stripping column; 4. an oxidation kettle; 5. an oxidant addition tank; 6. a dilute acid concentration tower; 7. nitrogen gas; 8. concentrated acid filter equipment.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Performing metal ion and SiO on dilute sulfuric acid, concentrated sulfuric acid and fresh concentrated sulfuric acid by adopting plasma emission spectrum analysis (ICP-MS) 2 Qualitative and quantitative analysis is carried out. And (4) qualitatively analyzing the filtered powder by using an FT-IR infrared spectrometer.
The raw material sulfuric acid treated by the embodiment of the invention is diluted sulfuric acid containing siloxane with the content of 64.6 weight percent, wherein the siloxane is SiO 2 The content was 8400 ppm.
Example 1
(1) Stripping: dilute siloxane-containing sulfuric acid having a sulfuric acid content of 64.6 wt.% was adjusted to 0.75m 3 The middle upper part of the graphite tower is added into the tower, and 4Kg/cm is respectively fed from the middle part (about 1/2 from the bottom of the tower) and the lower part (about 1/3 from the bottom of the tower) of the graphite tower 2 The stripping temperature is controlled at 130 ℃, and at high temperature, the siloxane impurities and organic matters in the dilute sulfuric acid are oxidized by utilizing the oxidation of the sulfuric acid per se to generate CO 2 、H 2 O and SiO 2 ；
(2) And (3) oxidation: dilute sulfuric acid after steam strippingAt 0.6m 3 The hydrogen peroxide solution is continuously conveyed into an oxidation kettle at a flow rate of/h, hydrogen peroxide solution (30 wt%) is used as an oxidant, and the hydrogen peroxide solution is 0.03m 3 The flow velocity is dripped into the oxidation kettle at the flow velocity of 0.6m when the oxidized dilute sulphuric acid flows out of the oxidation kettle 3 And/h, the oxidation reaction is to heat to 110 ℃, preserve heat for 1h, then heat to 130 ℃, preserve heat for 2h, and further remove siloxane impurities and organic matters.
(3) Concentrating: dilute sulfuric acid flowing out of the oxidation kettle is concentrated at the middle part of the concentration tower at the height of 0.56m 3 Flow rate of nitrogen at 20m 3 And/h is introduced from the lower part of the concentration tower, the concentration temperature is controlled at 180 ℃, and the moisture in the dilute sulfuric acid is brought out from the tower top.
(4) And (3) filtering: and filtering the concentrated sulfuric acid by adopting a polytetrafluoroethylene filter cloth to remove trace silicon dioxide powder, thus obtaining colorless and transparent concentrated sulfuric acid.
The product sulfuric acid was analyzed for acid content, COD value and silica by IPC-MS analysis after 12 hours of continuous production, see Table 1.
The obtained filtration residue was characterized by infrared method, and the results are shown in FIG. 2. In the infrared spectrum of FIG. 2, 3350cm -1 、1636cm -1 Is the association-OH peak; 2966. 1407cm -1 CH (1) 3 Peak 1265cm -1 Is Si-CH 3 A peak; 1021cm -1 Is the peak of Si-O; the left of 1021 peak has tail peak, which is characteristic peak of silicon oxygen group crosslinking, and tail of peak extends to 1265cm -1 ，782cm -1 Is Si-CH 3 Peak(s). It can be seen that the residue from the filtration in example 1 is silica formed by oxidation of siloxane and partially unoxidized siloxane or silicon hydroxy compound.
Example 2
(1) Stripping: diluted sulfuric acid of diluted siloxane-containing sulfuric acid having a sulfuric acid content of 64.6 wt.% was adjusted to 0.70m 3 The middle upper part of the graphite tower is added into the tower, and 6Kg/cm is respectively fed from the middle part and the lower part of the graphite tower 2 Low-pressure steam (entering position as figure 1) to control stripping temperature at 130 deg.C, and oxidizing siloxane impurities and organic substances in dilute sulfuric acid at high temperature by using sulfuric acid oxidationCO 2 、H 2 O and SiO 2 。
(2) And (3) oxidation: the diluted sulfuric acid after stripping is added at 0.5m 3 The mixture is continuously conveyed into an oxidation kettle at the flow rate of 0.04m by adopting hydrogen peroxide (30 percent) as an oxidant 3 The flow rate is dripped into the oxidation kettle at the flow rate of 0.59m 3 The oxidation reaction is carried out by firstly heating to 100 ℃, preserving heat for 0.5h, then heating to 140 ℃ and preserving heat for 2 h.
(3) Concentrating: dilute sulfuric acid flowing out of the oxidation kettle is concentrated by 0.57m from the middle part of the concentration tower 3 Flow rate of nitrogen gas is added at 20m 3 And/h is introduced from the lower part of the concentration tower, the concentration temperature is controlled at 190 ℃, and the moisture in the dilute sulfuric acid is brought out from the tower top.
(4) And (3) filtering: filtering the concentrated sulfuric acid by using polytetrafluoroethylene filter cloth, and removing trace silicon dioxide powder to obtain colorless and transparent concentrated sulfuric acid.
Example 3
(1) Diluted siloxane-containing sulfuric acid having a sulfuric acid content of 64.6 wt.% was adjusted to 0.73m 3 The middle upper part of the graphite tower is added into the tower, and 5Kg/cm is respectively introduced from the middle part and the lower part of the graphite tower 2 Low pressure steam (entering position as figure 1), stripping temperature controlled at 140 deg.C, and oxidation of siloxane impurities and organic substances in dilute sulfuric acid at high temperature by using oxidation of sulfuric acid itself to generate CO 2 、H 2 O and SiO 2 。
(2) The stripped dilute sulfuric acid is added at 0.58m 3 The hydrogen peroxide solution is continuously conveyed into an oxidation kettle at the flow rate of 0.03m by adopting a hydrogen peroxide solution (30 percent) oxidant 3 The flow rate is dripped into the oxidation kettle at the flow rate of 0.58m 3 And the oxidation reaction is carried out by firstly heating to 110 ℃, preserving heat for 1h, then heating to 140 ℃ and preserving heat for 2 h.
(3) The oxidized dilute sulfuric acid is concentrated from the middle part of the concentration tower by 0.55m 3 Flow rate of nitrogen gas is added at 20m 3 The water content in the dilute sulfuric acid is brought out from the top of the tower by introducing the dilute sulfuric acid from the lower part of the concentration tower, and controlling the concentration temperature to be 185 ℃.
(4) And filtering the concentrated sulfuric acid by adopting a polytetrafluoroethylene filter cloth to remove trace silicon dioxide powder, thus obtaining colorless and transparent concentrated sulfuric acid.
Example 4
(1) Steam stripping: dilute siloxane-containing sulfuric acid having a sulfuric acid content of 64.6 wt.% was adjusted to 0.75m 3 The upper part of the graphite tower (the upper part 1/3 of the graphite tower) is added into the tower, and 5Kg/cm is fed from the middle part of the graphite tower (the lower part 1/2 of the graphite tower) 2 8Kg/cm of low-pressure steam is introduced into the lower part (1/3 part at the lower part of the graphite tower) 2 The stripping temperature is controlled at 120 ℃, and at a high temperature, the siloxane impurities and organic matters in the dilute sulfuric acid are oxidized by the oxidation of the sulfuric acid to generate CO 2 、H 2 O and SiO 2 。
(2) And (3) oxidation: dilute sulfuric acid at 0.6m after stripping 3 The hydrogen peroxide solution is continuously conveyed into an oxidation kettle at the flow rate of 0.03m by adopting a hydrogen peroxide solution (30 percent) oxidant 3 The flow velocity is dripped into the oxidation kettle at the flow velocity of 0.6m when the oxidized dilute sulphuric acid flows out of the oxidation kettle 3 The oxidation reaction is carried out by firstly heating to 100 ℃, preserving heat for 1h, then heating to 160 ℃, and preserving heat for 2 h.
(3) Concentrating: the oxidized dilute sulfuric acid is concentrated from the middle part of the concentration tower by 0.56m 3 Flow rate of nitrogen gas is added at 20m 3 The water content in the dilute sulfuric acid is brought out from the top of the tower by introducing the dilute sulfuric acid from the lower part of the concentration tower, and controlling the concentration temperature at 180 ℃.
(4) And (3) filtering: and filtering the concentrated sulfuric acid by adopting a polytetrafluoroethylene filter cloth to remove trace silicon dioxide powder, thus obtaining colorless and transparent concentrated sulfuric acid.
Example 5
The other conditions were the same as in example 3 except that 2Kg/cm was fed from the middle part of the graphite column (the lower part 1/2 of the graphite column) in the step (1) 2 5Kg/cm of low-pressure steam is introduced into the lower part (1/3 part at the lower part of the graphite tower) 2 Low pressure steam.
Example 6
The other conditions were the same as in example 3 except for the step(1) Introducing 3Kg/cm of the solution from the middle part of the graphite tower (the lower part 1/2 of the graphite tower) 2 6Kg/cm of low-pressure steam is introduced into the lower part (1/3 part at the lower part of the graphite tower) 2 Low pressure steam.
Example 7
The other conditions were the same as in example 3 except that 3Kg/cm was fed from the middle part of the graphite column (the lower part 1/2 of the graphite column) in step (1) 2 The lower part (1/3 part of the lower part of the graphite tower) is filled with 7Kg/cm of low-pressure water vapor 2 Low pressure steam.
Example 8
The other conditions were the same as in example 6 except that in the step (2), the temperature of the oxidation reaction was directly raised to 140 ℃ and the temperature was maintained for 3 hours.
Comparative example 1
(1) Stripping: diluted siloxane-containing sulfuric acid having a sulfuric acid content of 64.6 wt.% was adjusted to 0.75m 3 The middle upper part of the graphite tower is added into the tower, and 4Kg/cm is introduced from the lower part of the graphite tower 2 The stripping temperature is controlled at 130 ℃, and the oxidation of the sulfuric acid is utilized to oxidize siloxane impurities and organic matters in the dilute sulfuric acid at high temperature;
(2) concentrating: the obtained sulfuric acid is fed from the middle part of the concentration tower at a flow rate of 0.56m 3 Flow rate of nitrogen gas is added at 20m 3 The water content in the dilute sulfuric acid is brought out from the top of the tower by introducing the dilute sulfuric acid from the lower part of the concentration tower, and controlling the concentration temperature at 180 ℃.
(3) And (3) filtering: and filtering the concentrated sulfuric acid by adopting a polytetrafluoroethylene filter cloth to remove trace silicon dioxide powder, thus obtaining colorless and transparent concentrated sulfuric acid.
The product sulfuric acid was analyzed for acid content, COD value and silica by IPC-MS analysis after 12 hours of continuous production, see Table 1.
Application example:
the concentrated sulfuric acid obtained in the above example 1 is used for the reaction of hydrogen chloride and methanol to generate methyl chloride, and in the step of drying methyl chloride, impurities such as water, ethyl chloride and the like in methyl chloride are dried and adsorbed, and after the obtained methyl chloride is detected, the water content is less than 2ppm, and the ethyl chloride content is less than 2ppm, which is equivalent to the impurity content in the methyl chloride after fresh concentrated sulfuric acid treatment.
TABLE 1
The experimental data show that the partial pressure feeding of low-pressure steam can enhance the desorption rate and improve the yield of the sulfuric acid; the invention is beneficial to improving the separation of organic siloxane by matching the sectional low-pressure steam with the oxidant under the action of gradient pressure, and effectively reduces COD and SiO in the recovered sulfuric acid 2 And (4) content. In addition, the staged temperature rise step of the oxidation step is beneficial to forward oxidation reaction, so that oxidation products are easier to take out, the generation of carbonization side reaction is reduced, the chromaticity of sulfuric acid is improved, and the oxidation efficiency is higher.
The invention obtains the concentration of more than 98 percent and the organic matter content COD of less than<120ppm (more preferably less than 80ppm), SiO 2 In an amount of less than<50ppm (more preferably less than 30ppm) clear, transparent, non-yellowing sulfuric acid. The treated sulfuric acid is recycled in the production of the methyl chloride, so that the production cost of the methyl chloride is reduced, the pollution to the environment is reduced, and obvious economic benefit and environmental protection benefit are achieved.
Claims (10)
1. A process for the continuous removal of siloxane from dilute sulfuric acid comprising the steps of:
(a) stripping: dilute sulphuric acid is added into a stripping tower from the upper part of the stripping tower, low-pressure steam is continuously introduced from different positions of the middle part and the lower part of the stripping tower, and oxidation reaction is carried out on organic matters and siloxane;
(b) and (3) oxidation: continuously feeding the stripped dilute sulfuric acid into an oxidation kettle, continuously adding an oxidant, and oxidizing residual organic matters and siloxane;
(c) concentrating: after oxidation, dilute sulfuric acid flowing out of the oxidation kettle is continuously added into the tower from the middle part of the concentration tower, nitrogen is introduced from the lower part of the concentration tower, and concentrated sulfuric acid is obtained at the tower kettle;
(d) and (3) filtering: continuously filtering the concentrated sulfuric acid to obtain colorless transparent concentrated sulfuric acid and white SiO 2 And (5) powder, and returning the obtained concentrated sulfuric acid to the methyl chloride production for continuous utilization.
2. The process of claim 1 wherein said stripping column of step (a) is a graphite column; the stripping temperature is 100-180 ℃, and preferably 110-140 ℃; the addition amount of dilute sulfuric acid in the stripping reaction is 0.1-5 m 3 H, preferably 0.5 to 1m 3 H; the low-pressure steam gas is water vapor.
3. The process according to claim 1 or 2, wherein the dilute sulfuric acid to be treated in step (a) has a sulfuric acid content of 60 to 75%, and a siloxane content of 4000 to 10000ppm (as SiO) 2 Meter).
4. The process of claim 1 or 2, wherein the low-pressure steam in step (a) is 2-8 Kg/cm at the middle and lower parts of the stripping tower 3 Preferably 4 to 6Kg/cm 3 The pressure of (2) is entered.
5. The process of claim 4, wherein the low-pressure steam is introduced from different positions in the middle and lower part of the stripping tower and at different pressures.
6. The process of claim 5, wherein 2 to 5Kg/cm is continuously fed into the middle of the stripping tower 3 Low-pressure steam is continuously fed into the lower part of the stripping tower at a rate of 5-8Kg/cm 3 The pressure of the low-pressure steam at the lower part is 1-3Kg/cm higher than that of the low-pressure steam at the middle part 3 。
7. The process of claim 1 or 2, wherein step (b) the oxidation reactor is an enamel or teflon lined reactor; the oxidant is at least one of hydrogen peroxide and potassium permanganate.
8. The process of claim 7, wherein the dilute sulfuric acid of step (b) is fed into the oxidation reactor at a flow rate of 0.1 to 3m 3 H, preferably 0.5 to 1m 3 H; the flow rate of the oxidant added into the oxidation kettle is 0.01-0.4 m 3 H, preferably 0.02 to 0.05m 3 H; the oxidation temperature is 100-160 ℃, and the temperature is kept for 1-3 h; the flow velocity of the dilute sulfuric acid flowing out of the oxidation kettle is 0.1-4 m 3 H, preferably 0.5 to 1m 3 /h。
9. The process of claim 1 or 2, wherein the concentration column of step (c) is at a temperature of 170 to 230 ℃, preferably 180 to 190 ℃; the adding flow rate of the dilute sulfuric acid is 0.1-5 m 3 H, preferably 0.5 to 1m 3 H; the nitrogen flow is 10-100 m 3 Preferably 20 to 30 m/h 3 /h。
10. The process as claimed in claim 1 or 2, wherein the oxidation in step (b) is carried out by heating to 100-120 ℃ and maintaining for 0.5-1h, and then heating to 130-160 ℃ and maintaining for 1-2 h.
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| US5683671A (en) * | 1996-01-11 | 1997-11-04 | Wacker-Chemie Gmbh | Process for purifying sulfuric acid |
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